The present invention relates to a command modulation system for generating commands to be sent to an external commanded device, for example, a satellite.
FIG. 1 illustrates the capabilities offered by typical existing command generator units. As shown in FIG. 1, the command generator unit 100 is arranged to receive inputs from a front panel interface and/or a computer interface link from an external data processing system 200. The hardware configuration of this conventional system consists of a microcomputer and peripheral processors housed in a single box of the command generator unit 100. Numeric keypads, control buttons and alphanumeric displays on the front panel make up the operator interface for local control, labelled front panel interface in FIG. 1. A serial interface port is used for computer control by an external processor 200, such an interface port being labelled computer interface link in FIG. 1. The parameters required to generate a command are either entered by an operator at the front panel or are received from the external data processing system 200. The commands originating from the external data processing system 200 may be stored in advance and then sent to the command generator unit 100 along the computer interface link. In accordance with the data received from the front panel or external data processing system, the command generator unit then generates the appropriate command sequences for transmission to the targeted system, e.g., a particular satellite.
The software used by the system of FIG. 1 is stored on a programmable ROM. This software processes the input from a local operator via the front panel controls, and/or the input from the external processor via the serial port. The software is written in assembly language and is very difficult to modify.
In addition, the command generator is custom designed to command only a specific type or types of known targeted system and can only produce a single type of output at a given time. This creates a problem in that, if plural known types of targeted systems are to be controlled simultaneously or new types of targeted systems are to be controlled, a respective number of command generators will be required.